John Miller Martin was born on 15 October 1904, son of Reverend John Martin. In 1943 he married Rosalind Julia Ross and they had one son. Martin was educated at the Edinburgh Academy, then Corpus Christie College, Oxford.

In 1927 Martin entered the Civil Service (Dominions Office) and was seconded to the Malayan Civil Service from 1931-1934. He became Secretary of the Palestine Royal Commission (chaired by Lord Peel) in 1936 and produced a report recommending that a solution be found for the disputes between the Arabs and the Jews by a partition of Palestine.

Martin was Private Secretary to the Prime Minister, Winston Churchill, from 1940-1945 (serving as Principal Private Secretary from 1941). As his Private Secretary, Martin travelled with Churchill on the significant journeys he made during the Second World War, to Washington, Cairo and Moscow. He was present at almost every summit meeting from the Atlantic Charter meeting in 1941 to Casablanca, Quebec, Teheran, Cairo and Yalta. From 1945-1956, Martin was Assistant Under-Secretary of State at the Colonial Office, becoming Deputy Under-Secretary of State in 1956 (to 1965). From 1965-1967 Martin was British High Commissioner in Malta. He died on 31 March 1991.